Ultrasonic fixture assembly for holding multiple ultrasonic transducers

ABSTRACT

An ultrasonic fixture assembly for holding multiple ultrasonic transducers includes a mounting support rod for attaching the fixture assembly to a manipulator of a ultrasonic inspection system. A plurality of transducer mounting blocks may be mounted to the support rod by an elongated mounting bar or a single transverse mounting block may be mounted to the support rod. Each of the transducer mounting blocks will have a channel formed therein for slidably receiving an ultrasonic transducer or if a single transverse mounting block is used a plurality of channels will be formed through the mounting block. A central channel or a central transducer mounting block is provided for receiving and retaining a longitudinal wave type ultrasonic transducer and other channels or transducer mounting blocks disposed on either side of the longitudinal transducer are formed to hold shearwave type transducers. The shear transducer mounting blocks are pivotably mounted to the elongated support rod to permit positioning the transducers to provide a predetermined angle of incidence of the ultrasonic signal. A mechanism is also provided to permit adjustment of the water path length between the transducer and the surface of the workpiece.

The government has rights in this invention pursuant to Contract No.F33657-85-C-2147 awarded by the Department of Air Force.

BACKGROUND OF THE INVENTION

The present invention relates to ultrasonic inspection of workpiecesand, more particularly, to a fixture assembly for holding multipleultrasonic transducers to provide substantially complete ultrasonicinspection of a portion of a workpiece in a single scanning operation orin a minimum number of scans to improve throughput and inspectionefficiency.

Typically, an ultrasonic inspection will involve a single transducermounted to an ultrasonic inspection system manipulator. This singletransducer, however, will inject or introduce ultrasonic energy or soundwaves into a workpiece under inspection only in one direction and alsoreceive a return or reflected signal or sound waves from a flaw ordefect along this same direction. For example, a longitudinal ultrasonicwave is typically introduced into the workpiece along a path normal tothe workpiece surface by a transducer and the transducer will receivereturn ultrasonic energy along this same normal path. Therefore, flawsor defects which are oriented substantially parallel to the workpiecesurface will be easily detected; however, flaws or defects which are notoriented substantially parallel to the workpiece surface, such as flawsoriented diagonally or substantially vertical relative to the workpiecesurface, may be missed or deemed insignificant because the defect orflaw is only inspected from one direction and may appear small andinsignificant in this direction.

Ultrasonic inspection from one direction or perspective, normal to theworkpiece surface, may be adequate for some workpieces; however, forthose components requiring a more complete and thorough inspection, itmay be desirable to introduce or inject a shearwave ultrasonic signalinto the workpiece at a predetermined angle of incidence to provide adesired angle of refraction of the ultrasonic energy upon entering theworkpiece. As many as three or more separate ultrasonic scans may thenbe required to substantially completely inspect a workpiece. Alongitudinal ultrasonic inspection scan is performed to pick up thoseflaws or defects oriented substantially parallel to the workpiecesurface and at least two circumferential shearwave ultrasonic inspectionscans may be required to pick up those flaws or defects which may beoriented substantially vertical or at some angle relative to the surfaceof the workpiece.

Phased array transducers are available for performing longitudinal andshearwave inspections in a single scan; however, these phased arraytransducers are more expensive than a single conventional transducer andif a single element of the array fails or goes bad, the entire phasedarray must be replaced rather than replacing a single transducer.

It is accordingly a primary object of the present invention to provide anovel fixture assembly for holding multiple ultrasonic transducers toprovide substantially complete ultrasonic inspection of a workpiece in asingle scanning operation or in a minimum number of required scanningoperations.

It is another object of the present invention to provide a novelultrasonic fixture assembly for holding multiple conventional ultrasonictransducers such that if one transducer fails or goes bad, only thatsingle bad transducer need be replaced.

It is a further object of the present invention to provide a novelultrasonic fixture assembly for holding multiple conventional ultrasonictransducers which is usable with conventionally known immersion typeultrasonic inspection systems and can be easily attached or detachedfrom the manipulators of such systems.

These and other objects of the present invention, together with thefeatures and advantages thereof, will become apparent from the followingspecification when read with the accompanying drawings.

SUMMARY OF THE INVENTION

In accordance with the present invention, an ultrasonic fixture assemblyfor holding multiple ultrasonic transducers includes an elongatedmounting bar and a central transducer mounting block or receptaclemounted in a central location of the elongated mounting bar. The centraltransducer mounting block has a first channel formed therein forreceiving a longitudinal wave type ultrasonic transducer. At least oneshear transducer mounting block or receptacle is pivotably mounted tothe elongated mounting bar on each side of the central transducermounting block. Each of the shear transducer mounting blocks has achannel formed therein for slidably receiving a shearwave typeultrasonic transducer, and each of the shear transducer mounting blocksis pivotably mounted to the elongated mounting bar to permit positioningof the shear transducer mounting block and the shearwave transducerdisposed

therein to provide a refracted shearwave at a predetermined angle ofrefraction within a workpiece under inspection. An adjustment means isassociated with each shear transducer mounting block for slidablyadjusting the position of the shearwave transducer within the channel,formed in the transducer mounting block, to permit positioning theshearwave transducer at a predetermined water path length between thetransducer and the workpiece under inspection for focusing ultrasonicenergy or sound waves from the shearwave transducer at a desiredlocation within the workpiece. The ultrasonic fixture assembly furtherincludes means for attaching the assembly to a manipulator of animmersion type ultrasonic inspection system.

In another embodiment of the present invention for performing anultrasonic inspection of a bore or hub, such as a bore formed in thecenter of a disk of a gas turbine engine, includes a central support rodfor attaching the fixture assembly to an immersion type ultrasonicinspection manipulator. A support member is attached at one end to thesupport rod and has a plurality of uniformly, circumferentially spacedopenings formed therein, each for receiving a respective ultrasonictransducer. A plurality of tubes are each slidably received in arespective one of the plurality of openings at an end of the supportmember opposite to the one end attached to the support rod. One end ofeach of the plurality of tubes is coupled to an operating face of anassociated one of the ultrasonic transducers and a distal end of each ofthe plurality of tubes has a mirror or reflective means mounted thereinfor reflecting ultrasonic energy from the associated ultrasonictransducer at a predetermined angle into the workpiece under inspection.A central tube is mounted to the support member for receiving a centralultrasonic transducer. The central tube has a centerline in alignmentwith a centerline of the central support rod and the support member. Thecenter transducer is used to align the fixture in the workpiece to beinspected to position each mirror or reflective device at an equaldistance from the workpiece.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a typical ultrasonic inspection systemwith which the ultrasonic fixture assembly of the present invention maybe used.

FIG. 2A is a detailed side elevation view of one embodiment of theultrasonic fixture assembly for holding multiple ultrasonic transducersin accordance with the present invention.

FIG. 2B is a top view of the ultrasonic fixture assembly of FIG. 2A.

FIG. 3 is a side elevation cross-sectional view of an ultrasonic fixtureassembly in accordance with another embodiment of the present invention.

FIG. 4A is a side elevation cross-sectional view of an ultrasonicfixture assembly in accordance with a further embodiment of the presentinvention for inspecting a bore or channel formed through a workpiece.

FIG. 4B is a cross-sectional view of the ultrasonic fixture assemblyshown in FIG. 4A taken along lines 4B.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring initially to FIG. 1, the ultrasonic fixture assembly 10 forholding multiple ultrasonic transducers may be used in conjunction withan immersion type ultrasonic inspection system 12. The ultrasonicinspection system 12 includes a manipulator 14 to which the fixtureassembly 10 is releasably attachable. The manipulator 14 includes X, Yand Z axes of motion to permit movement or scanning of the ultrasonicfixture assembly 10 and the ultrasonic transducers 16 held therein tosubstantially completely ultrasonically inspect a workpiece 18. Themanipulator 14 may also include gimbals 20 or universal joint to whichthe fixture assembly 10 is attached to facilitate scanning the surfaceof the workpiece 18.

The immersion type ultrasonic inspection system 12 also includes animmersion tank or reservoir 22 which is filled with water 24 and intowhich the workpiece 18 is immersed. The water provides improved couplingof the ultrasonic energy or sound waves between the transducers 16 andthe workpiece 18.

The system 12 may also include a turntable 26 or fixture arrangementupon which the workpiece 18 may be placed or fixtured, and the turntable26 may be rotated by the ultrasonic inspection system 12 to facilitatescanning of the flat surfaces of the workpiece 18.

The transducers 16 are electrically coupled by conductors 28 to anultrasonic fault detector 30, such as a KB-6000™ five-channelmultiplexer as manufactured by Krautkramer Branson or the like. Theelectrical conductors 28 are connected to a multiplexer 32 of theultrasonic fault detector 30 and the detector 30 also includes a pulsermodule 34 and a gate module 36. The ultrasonic fault detector 30 will,therefore, generate ultrasonic energy or sound waves which aretransmitted to the transducers 16 by the multiplexer 32 and electricalconductors 28 and receives return echoes from any defects or faults inthe workpiece 18 via the transducers 16, conductors 28 and themultiplexer 32. Generation of the ultrasonic waves or pulses by pulsermodule 34 is gated by the gate module 36 to permit receipt of anyultrasonic echoes caused by faults or defects in the workpiece 18between generation and transmission of each pulse of ultrasonic energyor signals by the detector 30.

The detector 30 is electrically connected to a display 38 which providesa visual image or indication of the fault and facilitates inidentification of the location of that fault within the workpiece 18.

Referring to FIG. 2A and 2B, in accordance with the present invention,the ultrasonic fixture assembly 10 includes an elongated mounting bar 38and a central transducer mounting block 40 or receptacle mounted in acentral location of the elongated mounting bar 38 by fasteners 42. Asbest shown in FIG. 2B, the central transducer mounting block 40 has afirst channel 44 or opening formed therein for slidably receiving alongitudinal wave type ultrasonic transducer 46. The longitudinal waveultrasonic transducer 46 may be positioned and retained in place by athumbscrew 52 which is received through a hole 54 formed through theelongated mounting bar 38 and threadedly received in another hole 56formed through the central mounting block 40 and open to channel 44 topermit tightening of the thumbscrew 52 against a longitudinal wavetransducer 46 inserted into the first channel 44. It should be notedthat the longitudinal wave transducer 46 can be easily exchanged orreplaced by another conventional type transducer if the originaltransducer fails or if a different type of transducer is desired to bemounted in the fixture assembly 10.

In accordance with the present invention, a sleeve 58 may be disposedwithin the first channel 44 to accommodate different sizes and types oftransducers.

In accordance with the present invention, at least one shear transducermounting block or receptacle is pivotably mounted to the elongatedmounting bar 38 on each side of the central transducer mounting block40. These shear transducer mounting blocks may be designated as the lefthand shear mounting block 60 and the right hand shear mounting block 62.Each of these shear transducer mounting blocks or receptacles 60 and 62have a channel 64 formed therein for slidably receiving a shearwave typeultrasonic transducer 66. As best shown in FIG. 2A, the channel 64 isformed through the shear mounting block 62 at a predetermined angle β tofacilitate injecting or introducing an ultrasonic sound wave or signaltransmitted by the transducer 66 into the workpiece 18 at a selectedangle of incidence θ to provide a desired angle of refraction α of theultrasonic sound wave or signal within the workpiece 18 for shearwaveultrasonic inspection of the interior of the workpiece 18.

The shear mounting blocks 60 and 62 are fastened to the elongatedmounting bar 38 by respective thumbscrews 68 and 69 which are receivedthrough holes 70 and 71 formed through the elongated mounting bar 38 andthreadedly received in holes 72 and 73 formed in the shear mountingblocks 60 and 62. The shear transducer mounting blocks 60 and 62 maythen be positioned by hand at a predetermined angle relative to theelongated mounting bar 38 and the central transducer mounting block 40and then held at this selected angle by tightening the respectivethumbscrews 68 and 69 to frictionally retain or hold the shear mountingblocks 60 and 62 in the selected position to provide the desired angleof incidence θ of the shearwave ultrasonic signal into the workpiece 18during an inspection operation.

In accordance with the present invention, an adjustment means 74 isassociated with each shear transducer mounting block 60 and 62 forslidably adjusting the position of the shearwave transducer 66 disposedwithin the channel 64 formed in the transducer mounting blocks 60 and 62to permit positioning of the shearwave transducer 66 at a predeterminedwater path length (L) defined as the distance between an operating face75 of the transducer 66 and the surface 77 of the workpiece 18 underinspection. The water path length (L) adjustment mechanism 74 permitsfocusing the ultrasonic energy or signal from the shearwave transducers66 and the longitudinal wave transducer 46 at a desired location orpoint 76 within the workpiece 18. Those skilled in the art will,therefore, recognize that the present invention is capable ofultrasonically detecting flaws within the workpiece 18 at various anglesof orientation relative to the surface 77 of the workpiece 18 withouthaving to perform multiple scans across the workpiece surface 77.

The water path length adjustment mechanism 74 includes a gear shaft 78retained within a housing 79 and rotatable therein. The housing 79 ismounted to the shear transducer mounting block 60 and 62 or isintegrally formed therewith. The gear shaft 78 has a gear spur 80mounted at one end thereof and a knurled knob 82 mounted at a distal endto permit turning of the gear shaft 78 with the thumb and forefinger.

In accordance with the present invention, a sleeve 84 is slidablyreceived within the channel 64 formed in each of the shear mountingblocks 60 and 62. A rack gear 86 is attached to the sleeve 84 andextends through a longitudinal slot 88 formed in a side of each of theshear transducer mounting blocks 60 and 62. The longitudinal slot 88 andthe rack gear 86 extending therethrough are oriented parallel to acenterline 89 of the channel 64 formed in each of the shear transducermounting blocks 60 and 62. The rack gear 86, the sleeve 84 and theshearwave transducer 66 disposed within the sleeve 84 will then slidewithin the shear transducer mounting block, either 60 or 62, in responseto rotation of the knurled knob 82 to permit positioning of theshearwave transducer 66 at the predetermined water path length (L) priorto an ultrasonic inspection.

A locking nut 90 may be threadedly received on the gear shaft 78 topermit locking the gear shaft 78 in place to prevent rotation thereofduring an inspection operation and to retain the water path at thepredetermined length (L) during an inspection operation. The gear shaftis retained or locked in position by tightening the locking nut 90against the housing 79 after the knob 82 is rotated to position theshearwave transducer 66 at the desired position within the channel 64.

In accordance with another embodiment of the present invention, aplurality of shearwave transducers 66 may be disposed on both sides ofthe longitudinal wave transducer 46 as shown in FIG. 3. Thisconfiguration further reduces the number of scans required tosubstantially completely inspect the workpiece 18 and permitscrisscrossing the ultrasonic sound waves or signals for a more completeinspection.

The ultrasonic fixture assembly 10' includes a central support shaft 92which is mountable to gimbals 20 or universal joint of the ultrasonicinspection system manipulator 14 (FIG. 1). A transverse shear transducerreceiver or mounting support member 94 is mounted to the support shaft92. The transverse mounting member 94 has a plurality of receptacles orchannels 96 formed therein on either side of the central transducermounting receptacle or channel 98. The channels 96 are preferably formedat a selected angle β relative to the longitudinal wave transducer toinject or introduce the shearwave signals into the workpiece at aselected angle of incidence θ to provide a desired refractive wave angleα within the workpiece 18.

The transverse mounting member 94 could also be formed in individualmounting blocks similar to that shown in FIG. 2A to permit adjustmentand preselection of the angle of incidence θ of the shearwave similar tothat described with respect to FIG. 2A. Additionally, the ultrasonicfixture assembly 10' may include a water path adjustment mechanism 74similar to that described with respect to reference numeral 74 in FIGS.2A and 2B.

A further embodiment of the present invention for inspecting a bore 100through a workpiece, such as the interior of a hub of a disk 18 for agas turbine engine or the like, is shown in FIGS. 4A and 4B. Theultrasonic fixture assembly 102 for inspecting the interior of a bore100 includes a central support rod 104 for attaching the fixtureassembly 102 to gimbals 20 or universal joint of the manipulator 14 ofan ultrasonic inspection system 12 (FIG. 1). A transducer receiver orsupport member 106 is attached at one end to the support rod 104 and hasa plurality of uniformly, circumferentially spaced receptacles oropenings 108, each for respectively receiving a different ultrasonictransducer 110. A tube 112 is respectively slidably received in each ofsaid plurality of openings 108 at an end 114 of the transducer supportmember 108 opposite to the end at which the central support rod 104 isattached to the transducer support member 106. One end of each of thetubes 112 is coupled to an operating face 116 of the associatedultrasonic transducer 110 and a distal end 118 of the tube 112 has amirror 120 or reflective device mounted therein at a predetermined angleto reflect the ultrasonic energy or sound waves from the ultrasonictransducer 110 into the workpiece 18 at a selected angle of incidence.

A central receptacle or opening 122 is also formed in the transducersupport member 106 for receiving a center ultrasonic transducer 124(FIG. 4B). A central tube 126 may also be coupled to the centraltransducer 124. The central opening 122 has a centerline 123 which isaligned with a centerline 125 (FIG. 4A) of the central support rod 104and the transducer support member 106. The center transducer 124 is thenused to align the fixture 102 in a bore 100 of a workpiece 118 to beinspected in proper alignment such that each mirror 120 of theuniformly, circumferentially spaced tubes 112 is spaced at an equaldistance from the workpiece 18.

A thumbscrew 128 is associated with each opening 108 in the transducersupport member 106 to permit securing each of the transducers 110 andthe associated tube 112 in a predetermined position within thetransducer support member opening 108.

It will be readily understood by those skilled in the art that thepresent invention is not limited to the specific embodiments describedand illustrated herein. Different embodiments and illustrations besidesthose shown herein and described as well as variations, modificationsand equivalent arrangements will now be apparent or will be reasonablysuggested by the foregoing specification and drawings, without departingfrom the substance or scope of the invention. While the presentinvention has been described herein in detail in relation to itspreferred embodiments, it is to be understood that this disclosure isonly illustrative and exemplary of the present invention and is mademerely for purposes of providing a full and enabling disclosure of theinvention. Accordingly, it is intended that the invention be limitedonly by the spirit and scope of the claims appended hereto.

What is claimed is:
 1. An ultrasonic fixture assembly for holdingmultiple ultrasonic transducers to provide longitudinal and shearwaveultrasonic inspection of a workpiece during a single scanning operation,said fixture assembly comprising:an elongated mounting bar; a centraltransducer mounting block mounted in a central location of saidelongated mounting bar, said central transducer mounting block having afirst channel formed therein for slidably receiving a longitudinal wavetype ultrasonic transducer and a second channel formed therein forreceiving a support bar for attaching said fixture assembly to animmersion type ultrasonic inspection manipulator; at least one sheartransducer mounting block pivotably mounted to said elongated mountingbar on one side of said central transducer mounting block, said sheartransducer mounting block having a channel formed therein for slidablyreceiving a shearwave tape ultrasonic transducer, and said sheartransducer mounting block being pivotably mounted to said elongatedmounting bar to permit positioning of said shear transducer mountingblock and the shearwave transducer receivable therein to provide arefracted shearwave at a predetermined angle of refraction; andadjustment means associated with said shear transducer mounting blockfor slidably adjusting the position of the shearwave transducerreceivable within the channel formed in said transducer mounting blockto permit positioning said shearwave transducer at a predetermined waterpath length between said shearwave transducer and the workpiece underinspection for focusing ultrasonic energy from the shearwave transducerat a desired location within the workpiece.
 2. The ultrasonic fixtureassembly of claim 1, further comprising a sleeve disposed in the channelformed in said shear transducer mounting block for holding the shearwavetransducer;and said adjustment means comprising:a rack gear attached tosaid sleeve and extending through a longitudinal slot formed in a sideof said shear transducer mounting block, said longitudinal slot and saidrack gear being oriented parallel to a centerline of the channel formedin said shear transducer mounting block; and a gear shaft rotatablymounted to said shear transducer mounting block, said gear shaft havinga gear spur mounted at one end which meshes with said rack gear and aknob mounted at a distal end, said gear spur being rotated in responseto said knob being turned to cause said rack gear, said sleeve and saidshearwave transducer disposed within said sleeve to slide within theshear transducer mounting block channel to permit positioning theshearwave transducer at the predetermined water path length prior to anultrasonic inspection.
 3. The ultrasonic fixture assembly of claim 2,further comprising means for preventing said gear shaft from rotatingduring an inspection operation and for retaining the water path at thepredetermined length during the ultrasonic inspection.
 4. The ultrasonicfixture assembly of claim 1, further comprising means associated withsaid shear transducer mounting block for positioning and retaining saidshear transducer mounting block at a selected angle relative to saidelongated mounting bar to provide the refracted shearwave from theshearwave transducer at the predetermined angle of refraction.
 5. Theultrasonic fixture assembly of claim 4, wherein said positioning andretaining means comprises a threaded thumbscrew extending through a holeformed in said elongated mounting bar and threadedly received in amatingly threaded hole formed in said shear transducer mounting block,said shear transducer mounting block being positioned at the selectedangle and said thumbscrew being tightened to draw said shear transducermounting block tightly against said elongated mounting bar to positionand retain said shear mounting block at the selected angle during aninspection operation.
 6. The ultrasonic fixture assembly of claim 1,further comprising a plurality of said shear transducer mounting blocksand respective adjustment means mounted on said mounting bar, and atleast one of said shear transducer mounting blocks being disposed oneach opposite side of said central transducer mounting block.
 7. Theultrasonic fixture assembly of claim 6, wherein each of said sheartransducer mounting blocks has a respective channel formed therein forslidably receiving a respective shearwave type ultrasonic transducer,each of said channels being formed at a predetermined angle to causeultrasonic energy from the shearwave transducers on opposite sides ofthe longitudinal transducer to intersect.
 8. An ultrasonic fixtureassembly for holding multiple ultrasonic transducers, comprising:acentral longitudinal receptacle for receiving a longitudinal wave typeultrasonic transducer; a plurality of shear receptacles, at least one oneach opposite side of said central receptacle for receiving a respectiveshearwave type ultrasonic transducer, each of said shear receptaclesbeing oriented at a predetermined angle to cause ultrasonic energy fromthe shearwave ultrasonic transducers on opposite sides of thelongitudinal transducer to intersect within a workpiece underinspection; and means for adjusting a water path length between each ofthe longitudinal and shearwave type transducers and the workpiece. 9.The ultrasonic fixture assembly of claim 8, further comprising means foradjusting the predetermined angle of each of said shear receptacles.